What is Addison’s disease?
Also known as hypoadrenocorticism, Addison’s disease is a potentially life-threatening deficiency in hormones produced by the adrenal glands.
These glands, located near the kidney, produce hormones such as cortisol, a stress hormone, and aldosterone, which regulates salt, sugar and water balance in the body.
Dogs with insufficient levels of these hormones can become very unwell. Addison’s disease is more common in young to middle-aged dogs, particularly females.
What are the symptoms of Addison's in dogs?
Signs of Addison’s in dogs typically include lethargy, lack of appetite, depression, reluctance to exercise, vomiting and diarrhoea. These may appear very suddenly and can be both intermittent and severe. Dogs suffering from the illness may also drink more and urinate more. It has been known for dogs with Addison’s to arrive at the vets extremely ill, in shock or collapsed, and almost in a coma. This is called an Addisonian crisis.
What causes Addison's in dogs?
Addison’s disease is usually caused by immune-mediated destruction of the adrenal glands. This means the dog’s immune system has become compromised and the adrenal glands have been damaged or attacked and therefore cannot produce enough hormones. Other less common causes include cancer and infections.
There are two types of Addison’s. The most common, or typical, form is due to lack of both corticosteroids and mineralocorticoids and can be fatal. The less common, or atypical, form of Addison’s is due to a lack of corticosteroids alone.
How is Addison's disease in dogs diagnosed?
Dogs with suspected Addison’s often have a severe lack of body fluids, including dehydration, low sodium, high potassium, low blood sugar and high calcium. Diagnostic tests on kidneys may also show up as abnormal.
In general, these clinical signs are enough for the vet to start treatment until a final diagnosis is established.
A final diagnosis is made if and when the vet establishes either very low levels of steroids in the blood or by performing an ACTH stimulation test with a documented ‘no increase’ in the production of steroids.
Is stress a factor in Addison's disease?
One of the reasons adrenal glands produce cortisol is to help dogs deal with stress. If a dog cannot make enough of this hormone they may not be able to deal with stress or their symptoms will worsen when they are stressed. Stress is generally caused by a change in the dog’s routine. It’s important to minimise stress from your dog’s life and to consider increasing their medication at times of high stress.
What is the treatment for Addison's?
Dogs who are very sick with Addison’s will require fluids via a drip as well as medication to help increase sodium and lower potassium. High levels of potassium can cause heart arrhythmias and lead to death. It’s likely this medication will be given as injections in the early stages of treatment. This is usually changed to a daily pill as soon as the dog is feeling better and has their appetite back.
Medication for Addison’s disease is needed for life and patients typically to do very well on it. Cases of typical Addison’s are treated with a combination of corticosteroids (prednisolone) and mineralocorticoids (fludrocortisone). Dogs who only lack the corticosteroids, atypical cases, are only given prednisolone and monitored, although over time they might end up needing fludrocortisone too.
What is the prognosis?
As long as dogs receive the appropriate treatment, they can live a long and happy life. It’s worth noting, however, that anything that prevents the dog from getting their medication is likely to result in an emergency. Dogs with Addison’s have a lower immune system so even minor illnesses can be life-threatening and may not respond to treatment. The stress brought on by such an illness can lead rapidly to an Addisonian crisis.